The present invention is generally directed to a circuit for providing a temperature insensitive voltage, and more particularly to a bandgap voltage generator.
Bandgap voltage generators provide a specific low voltage that is desirably insensitive to temperature. The voltage is typically equal to the bandgap potential of silicon at 0.degree. Kelvin, approximately 1.2 volts, although other low voltages may be provided. The generated voltage is used in variety of applications, including CMOS integrated circuits.
Bandgap generators, such as disclosed in U.S. Pat. No. 5,144,223 to Gillingham, have moved away from the use of amplifiers because of the current they consume, especially in low power operations. The present invention solves the current consumption problem and is able to use an amplifier efficiently in a 5 volt system.
Accordingly, it is an object of the present invention to provide a novel circuit for providing a voltage that is insensitive to temperature that obviates the problems of the prior art.
It is another object of the present invention to provide a novel circuit for generating a bandgap voltage in which a feedback loop for an amplifier includes a high impedance output current mirror for controlling the current across a resistor.
It is yet another object of the present invention to provide a novel bandgap generator in which an amplifier feedback loop includes a high impedance output current mirror for providing proportional currents to a pair of resistors that are connected to the amplifier, where one resistor feeds a temperature sensitive voltage to a first amplifier input, and a voltage is provided to a second amplifier input from a combination of a temperature sensitive voltage across a second transistor from which the bandgap voltage may be tapped and an offsetting voltage.
It is still another object of the present invention to provide a novel circuit for providing a bandgap voltage for a five volt system, the circuit having a pair of bipolar transistors with a common collector and bases connected to a reference voltage source, a first resistor connected in series with an emitter of a first of the bipolar transistors, an amplifier with a first terminal connected to the first resistor and a second terminal connected to an emitter of a second bipolar transistor, a second resistor connected in series with an emitter of the second bipolar transistor, the second resistor being tapped for providing a bandgap voltage, and in which an amplifier feedback loop provides proportional currents to the two resistors.
It is a further object of the present invention to provide a novel circuit for generating a bandgap voltage in which a feedback loop for an amplifier includes a high impedance output current mirror that is controlled by series connected field effect transistors that provide control signals to the gates of field effect transistors in the current mirror.
It is yet a further object of the present invention to provide a novel circuit for generating a bandgap voltage in which a feedback loop for an amplifier includes a current mirror that is controlled by an array of series connected field effect transistors, the current mirror including two pairs of field effect transistors for providing a high impedance output and that have their gates connected to the controlling field effect transistors.
It is still a further object of the present invention to provide a novel circuit for generating a bandgap voltage for biasing an entire semiconductor chip that is insensitive to temperature, and is independent of power supply variations and of trimming of the bandgap.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.